The invention relates to refrigerant handling systems for recycling refrigerant from and recharging refrigerant to a refrigeration unit. The invention has particular application to systems of the type designed for servicing automotive air conditioners and which include a refrigerant identifier.
Refrigerant handling systems for servicing automotive air conditioners are well known. Such systems typically can be operated to recover or remove refrigerant from an air conditioner to permit servicing of the air conditioner, to recycle the recovered refrigerant by removing various contaminants therefrom, and then to recharge the refrigerant to the air conditioner after servicing is completed. Such systems are typically connected to an automotive air conditioner by two hoses, respectively connected to the high-pressure and low-pressure sides of the air conditioner compressor. These hoses have a predetermined fixed length sufficient to permit them to reach the air conditioner when the refrigerant rehandling unit is positioned alongside the vehicle.
Several different types of refrigerants are commonly used in automotive air conditioners. It is important that these refrigerants not be contaminated by contact with one another or with other types of contaminants. Thus, identifiers are used to identify the type of refrigerant in the air conditioner and its purity level. A given refrigerant handling system is typically used with only one type of refrigerant, and the identifier determines whether the refrigerant being recovered from the vehicle is of the proper type and purity.
However, in such prior systems, the identifier is coupled in the recovery path and, in the event that the identified refrigerant is of the wrong type or is contaminated, the plumbing of the refrigerant handling system has already been contaminated. In this event, such prior systems would have to be shut down, disconnected from the vehicle and then connected to a separate scavenging unit to clear the system by removing the contamination.
Also, certain automotive manufacturer service specifications specify the precise amount of refrigerant to be recharged to the air conditioner after it is serviced, which amount must be accurate within a tolerance level, such as one ounce. The amount recharged is determined by comparing the weights of the refrigerant tank before and after recharge. But this only determines the amount which has left the recovery tank, and that amount will differ from the amount which enters the air conditioner by the amount left in the intervening conduits and hoses. Thus, the refrigerant handling system recharge protocol must compensate for this difference, and must also compensate for ambient conditions, such as temperature and pressure, which can affect the volume of the refrigerant. This compensation requires the use of very complicated algorithms in the system processor during the calibration procedure. This effectively precludes varying the length of the service hoses between the refrigerant handling system and the air conditioner, since every time the hose length is changed the system would have to be recalibrated and/or the software algorithm would have to be changed.